Containers made of flexible or semi-rigid plastic material are already known in the art, comprising such materials as polyvinyl chloride, polyethylene, polypropylene and polycarbonate. Many types of liquid soaps and detergents for personal hygiene are supplied in such containers, which are designed to be inserted into dispensers provided with hand-actuated pumps. Many of the dispensers are designed such that, as liquid is pumped from the container, air back flows into the container to replace the displaced liquid. This can lead to degradation and shortened lifetime of the liquid due, for example, to oxidation and contamination. In addition, evaporation of the liquid occurs, causing thickening of the soap and may result in blockages of the pumping mechanism.
An alternative is to provide a collapsible container, such as described in U.S. Pat. No. 5,556,005. In this patent, there is described a container and valve assembly combination whereby as liquid is dispensed from the container by vacuum or suction, the air-tight seal at the valve assembly prevents air from being drawn into the container so that the container slowly collapses as the liquid volume decreases. Collapsible containers such as described in the referenced patent reduce exposure of the liquid soap to air by collapsing the container, which decreases oxidation and contamination of soaps contained therein, thus increasing the useful life of the liquid.
A problem occurs when attempting to design a collapsible container for use in soap dispensers, such as that described in U.S. Pat. No. 5,556,005. Specifically, when the liquid soap is filled in the container, the high speed filling process tends to cause bulging in the container side panels and/or front and back panels. This bulging prevents or hampers high speed filling of the containers and creates fit problems when such bulging containers are installed in dispenser housings.
There is thus a need to provide a collapsible container for use in soap dispenser or other liquid dispensers such that the container efficiently collapses upon evacuation of the liquid contents and furthermore does not unduly bulge during filling of the container with the liquid contents.